Low fat? Low carb? Vegan? Crash diets? Diet soda? Exercise? What’s the most effective way to lose weight? Here’s a look at what 2014’s weight loss studies showed us, including one cautionary tale for all dieters.

The diet battle of the year

What’s better, low carb or low fat for weight loss? A meta-analysis published in JAMA in September suggested: Oh, heck, just follow a regimen. Though low carb very slightly outclassed low fat for weight loss over a course of months, the differences were minimal, and both approaches worked.

Low-carb dieters trump low-fat eaters, at least in this study

But another study, published the same month in the Annals of Internal Medicine, found that low-carb dieters fared much better than those who followed a low-fat diet and showed better results on blood tests that indicate cardiovascular health. This study by Tulane University researchers was especially noteworthy because unlike most weight-loss studies, it randomly assigned subjects one group or the other, drastically reducing the chances that there were differences other than diet that accounted for the greater weight loss.

It's not always easy for restaurant-goers to figure out which options are the least fattening. Some diners at a California Pizza Kitchen, for example, might order the Moroccan-spiced chicken salad rather than a pizza, unaware that the salad packs 1,500 calories — three-fourths of the recommended...

(The Times editorial board)

Love carbs and (living) animals?

In case the confusion level isn’t higher than your carb intake by now, a University of South Carolina study published in November in the International Journal of Applied and Basic Nutritional Sciences found the greatest weight loss on a high-carbohydrate vegan diet that eschewed all animal products including dairy. The subjects, all university students, were randomly assigned to their eating regimens in this study as well. But support groups that included peer pressure to perform well also played a part in the study.

You’ll see this over and over; no matter what scientists find, the belief persists. But once again this year, a correlational study suggests crash diets might be more successful than the slow-and-steady sort. The October study in the Lancet Diabetes & Endocrinology found that over time, both types of dieters regained an average of 71% of the weight lost, but crash dieters were more likely to have reached their goals in the first place.

Diet more important than aerobics?

Another study cast doubt on a widely held belief about weight loss -- that aerobic exercise is important to the effort. Research at Arizona State University in Phoenix, published in the October issue of the Journal of Strength and Conditioning Research, found that women who engaged in a regular regimen of supervised treadmill exercise, without changing their previous eating habits, tended to gain weight, largely in the form of fat, instead of losing it, though it’s important to note that they also became more physically fit. Some of the subjects did lose weight and fat, and the scientists think that observing the effect of diet regimens and exercise after a few weeks can help predict which women would be most likely helped in their weight-loss efforts by regular aerobic exercise. The study followed a body of previous research that found that aerobic exercise did not seem to lead to the kind of weight loss that would have been expected from the calories burned.

More sad news about obesity

This one won’t surprise anyone. The U.S. Centers for Disease Control and Prevention reported in October that depression and obesity are strongly linked, and the worse the depression, the worse the obesity (or possibly the other way around.)

Good news/bad news about gastric bypass surgery

For those who choose more aggressive paths to weight loss, an October JAMA Surgery study found that patients who underwent gastric bypass surgery lost more weight than those who chose gastric banding. However, the bypass group suffered more complications, including blood clots in the legs and lungs.

Breakfast may not be the most important meal of the day

Contrary to popular belief and the lectures of who knows how many mothers, breakfast doesn’t appear to be the most important meal of the day, at least when it comes to weight loss, according to University of Alabama researchers. The scientists randomly assigned subjects to eat or not eat breakfast, and they found that it made no real difference to weight loss if dieters skipped the meal altogether. But they also didn’t examine what people ate for breakfast and said that it would take more research to find out whether eating certain kinds of breakfasts might actually make a difference. They published their findings in August in the American Journal of Clinical Nutrition. Another study at about the same time at the University of Bath found pretty much the same thing.

Diet sodas may not be the best option for dieters

We heard plenty during 2014 about the empty calories we consume in sugary sodas without even feeling fuller from all that intake, but one of the more controversial questions has been whether diet sodas are healthier for people. There are studies on both sides, but one of the most intriguing pieces of research -- conducted on mice -- says it might depend on the individual. The study found that unlike sugary sodas, artificial sweeteners change gut bacteria in ways that affect how we digest and metabolize food. And those changes might make some people more prone to weight gain and diabetes. Remember that these are results on mice fed large amounts of artificial sweetener, not on humans who drink a can or two of diet soda a day, but, as the researchers said, the results call for a closer examination of how artificial sweeteners act on the human body and on weight loss.

The most important weight-loss research news

Perhaps the most important weight-loss research news of all is the item that reminds us to be skeptical of studies (perhaps especially when they’re touted by Dr. Oz), to look for studies that appear in respected publications, be aware of who’s funding the study and what they might have to gain from it, and even when it comes to the best-conducted research, to remember that weight-loss studies are usually just adding pieces to a complex and largely incomplete picture of how weight is gained and lost -- they are not a signal to adopt one change after another based on a single finding.

In October, researchers retracted a previously published study that purported to find that pills made from green coffee beans led to remarkable weight loss.

The study was conducted in India and funded by a company called Applied Food Sciences -- which sells the pills. But it was written and published by two professors at the University of Scranton who were hired by Applied Food Sciences. The coffee-bean phenomenon fell apart after the Federal Trade Commission brought forth evidence of falsified information in the study -- and after U.S. consumers spent hefty sums on a product not known to have any weight-loss usefulness. Shame on the company, the researchers, the professors who allowed their reputations and that of their university be hired out for bucks, and of course on Dr. Oz. And thanks to smart and aggressive regulators who knew when to step in.